A heat distributing system typically has a condenser unit which includes tubing to conduct fluids. There have been proposed different ways of cleaning the inside of such tubing to prevent the build up of dirt or other unwanted deposits Inside the tubing as the fluids travel through the tubing.
One proposed way is the use of cleaning balls made of rubber or spongy material which have a diameter slightly larger than the tubing so that when they travel through the tubing with the fluid, the balls are compressed. In this way, the balls are made to rub against the walls of the tubing so as to keep the walls clean and substantially free from deposits. Generally, the balls and the fluid are passed through the tubing, in the direction of the fluid flow, from the upstream side to the downstream side of the tubing. The balls are then separated from the fluid at the downstream side and then recirculated back to the upstream side of the tubing. A pump, such as that described in patent document U.S. Pat. No. 6,070,652, typically provides the means to recirculate the balls. However, a disadvantage of using a pump to recirculate the balls is that the pump is susceptible to malfunctioning and such a system usually requires considerable downtime for maintenance and repair.
To overcome the above disadvantage, there has been proposed a cleaning system that does not use a pump to recirculate the balls, an example of which is described in patent document U.S. Pat. No. 5,592,990. In this prior art, the recirculating means comprises a housing disposed between the upstream and downstream side of the tubing. The housing includes an apertured partition which divides the housing into a upper compartment and a lower compartment. When the balls are recirculated and collected by this housing, the partition permits the fluid to pass through to the lower compartment while keeping the balls in the upper compartment. The housing further comprises a first passageway which connects one end of the upper compartment to the downstream side of the tubing, a second and third passageway connecting the other end of the upper compartment to a first and second section in the upstream side of the tubing such that the second section of the tubing has a slightly lower pressure compared to the pressure at the first section but higher than that at the downstream side of the tubing. The housing also comprises a fourth passageway connecting the lower compartment to a source of lower pressure than that in any of three other passageways. The cleaning system disclosed in this prior art also has a plurality of valves arranged to control the fluid flow along the different passageways described above. A disadvantage of this prior art is the complexity of the design which requires a sequence of actions to close and open the plurality of valves to recirculate the balls. In addition, to draw the balls into the housing, the valve disposed at the fourth passageway must be opened and this may discharge the fluid. As a result, the fluid is wasted each time the balls are recirculated and the cost of maintaining such a system may be relatively expensive.
It is an object of this invention to provide a cleaning system which alleviates at least one of the disadvantages of the prior art.